Synthesize, isolate, purify, analyze, and supply small quantities of NCI-selected radioactive retinoids for use as tracers in metabolic studies, both in vivo and in vivo. Specifically: five to 50 mCi of each radiolabeled material will be produced at specific activities of one to two Ci/mmole (3H) and 10 to 100 mCI/mmole (14C), depending on NCI needs and methods of preparation; compounds will be furnished to the NCI Carcinogenesis Research Program which will be directly suitable for research purposes without further purification. Data documenting the radiochemical and chemical purity of each product will be supplied to the Project Officer prior to shipment along with a small sample of the radioactive compound on which NCI personnel can determine the purity.